If flatulence is defined as discomfort arising from an abnormal amount of gas in the stomach with or without eructation of gas, it is a symptom in many conditions. It is so frequently placed in the front of the patient's complaint, that it deserves separate consideration, especially as dietetic measures are generally needed in treatment. For so common a matter, its origin is curiously obscure. In some cases the origin of the gas has never been demonstrated. The cause is often to be found in faulty eating and errors of diet, and these cases are easily rectified, though they are not so easily explained. In other cases the origin is a matter of guess-work and the whole subject presents difficulties.

(1) A considerable amount of air is swallowed with food and saliva. Under normal conditions no discomfort results and presumably the air is passed on into the bowel, though there is no evidence to disprove that it may not also be absorbed by the stomach-wall. Such absorption of gas certainly occurs in the intestine. Flatulence, however, as defined above may be produced from air so swallowed. It is commonly a result of the quick eating of a large meal, especially if large quantities of fluid are taken. A feeling of distension and some gaseous eructation may then be experienced long before the meal is over. Whether more air is then swallowed or whether its normal disposal is prevented by closure of the pylorus or otherwise is uncertain. The remedy is obvious. It is especially important to diminish the amount of fluid taken at meals.

Some people, mostly middle-aged women, are plagued with gastric noises and eructations apart from meals and at awkward times. It has been thought that they have acquired the habit of swallowing air apart from saliva. I have seen nothing to support this theory, and I believe that the gas has the same origin as in some obscure conditions mentioned later. But one cannot help thinking that in these women the noise is quite out of proportion to the amount of gas, and it may be produced in the oesophagus.

(2) In health some CO2 is added to the air in the stomach by the action of hydrochloric acid on the carbonates of the food and saliva. In disease, especially in conditions of motor insufficiency, gastrectasis and chronic gastritis, this is greatly increased by the fermentation of carbo-hydrates, especially the butyric acid fermentation of which hydrogen also is a product. In slight degree it is a common complaint in the obese. The dietetic treatment has been already described.

(3) In hyperacidity flatulence is often a prominent feature, but its origin is not quite certain. It is possible that when, as often happens in this condition, the flow of saliva is increased the amount of swallowed air may also be increased. It is possible also that there is an increased evolution of gas by the action of hydrochloric acid on the saliva, for as was shown by Sir William Roberts, the saliva in hyperacidity is more alkaline than in health. He found the alkalinity equal to 0.04 per cent of hydrochloric acid. It is not unlikely that gas is regurgitated into the stomach from the duodenum, being evolved there by the action of the excessively acid chyme on the carbonates of the bile and pancreatic secretion. Carbo-hydrate-fermentation may add its quota to the flatulence, for considerable stagnation of the stomach-contents may occur in hyperacidity, and fermentation is always more influenced by delay of food in the stomach than by the degree of acidity reached. In the treatment of hyperacidity these considerations should be borne in mind.

(4) Putrefactive decomposition of protein, which is a normal process in the colon and which occasionally occurs under pathological conditions in the small intestine, is rarely met with in the stomach. It is limited to cases of long-standing and neglected gastrectasis. The gases formed are marsh-gas, hydrogen, carbon dioxide, and sulphuretted hydrogen. It is possible that in some such cases the gases may enter the stomach from the bowels. The diagnosis is not difficult and the line of treatment is plain.

(5) There is a group of conditions, which present flatulence as a great source of trouble but which perhaps have little else in common. In all of these the stomach may quickly or suddenly become distended with gas. Sometimes only a subjective feeling of distension is produced : more commonly there is actual distension and not only does the area of stomach-resonance encroach on the cardiac area, but the epigastrium is protruded and clothes must be loosened. It may be taken as certain that the gas in these cases is not evolved from any food in the stomach. Its evolution is too rapid, it has no constant relation to meals, it may occur with an empty stomach, and it is sometimes a regular precursor of other phenomena. It is possible that the gas is discharged into the stomach from the bowel, but this is very unlikely inasmuch as there is no evidence in such cases of any intestinal disorder which could lead to such an abundant development of gas. I think there is no other possible explanation than that the gas is CO2 derived from the venous blood in the stomach-wall, and in the whole group there exist indications of some form of neurosis or nervous disturbance in which the vagus and its branches share.

This form of sudden and voluminous flatulence occurs in some people of nervous temperament, as an isolated phenomenon, occurring at odd times and having no apparent relation with any previous factor or any event to follow. The type of person so affected is, I think, the industrious woman who takes life hardly from choice or necessity. But such an occurrence may be associated with a sense of cardiac oppression and pain or aching in the left arm. It is also a well known precursor of an attack of asthma. I have seen a nurse in whom it often occurred without other symptoms, though it was sometimes followed by a mild pseudo-angina and sometimes by an attack of true asthma.

This same trouble, though less sudden and more lasting, is not uncommon in cardiac failure from any cause. Perhaps the associated venous hyperaemia of the stomach may contribute to it. But it occurs also in valvular disease, both of rheumatic and of arterio-sclerotic origin, when there is no sign of cardiac failure and when nothing in the history or appearance of the patient would lead one to suspect the existence of such disease. A still more serious matter is its occurrence in connexion with true angina. It may be the first symptom of an attack, and if the pain is placed centrally both physician and patient may fall into the error of regarding the case as one of gastric disorder. Apart from true angina, it occurs also in old people with considerable arterio-sclerosis, often in nocturnal attacks, and queer flatulence in such cases should always be treated with respect.

The importance of this group from the dietetic point of view lies in the negative facts that the gas is not evolved from carbohydrates and that radical alteration of the diet is useless. Such treatment as is possible consists in the institution of small simple mixed meals, eaten slowly without excess of fluid, and followed by rest. The evening meal should be a light one. In the old man, who through ignorance retains the eating habits of his youth, some relief may be expected.